Hi folks,

I don't have any CNC machines yet and I am just learning Gcode, but I figured it
would help to look at code examples and try to plot them with the backplot in EMC.

The install was cake (I guess cause I teach Linux) but I can't get consistent results out of the backplot feature. Specifically the "3D_chips.ngc" file seems to plot way off the screen an when I try to scroll, the backplot screen is blank. Also is there anyway to just to do a quick backplot without attempting to control the machine? In other words how do I speed things up?

I'm using sim.run from a shell window
and the BDI-TNG which uses RTAI and Redhat 7.2 on a PII600 with 128M of RAM.

Thanks
Brian

Hi Brian,

I am not at all familiar with the software you are using, but there are a few conventions that must be known and observed for successful backplotting in general.

Most often, backplot software reads only G00, G01, G02, G03 and G90 (absolute coordinate mode) or G91 (incremental coordinate mode). Usually, a G90 or G91 should be posted very early in the code before any machine movements are made. This is essential information for the backplot to be correct.

Secondly, arc movement commands (with G02 or G03 words) can legally use either incremental arc center coordinates or absolute arc center coordinates, depending on the controller, and what mode it is running in (G90 or G91). There is a vast difference in the output of the backplot if the backplot software arc interpreter does not match the original arc center coordinates of the post that created the gcode file.

So if the backplotter has the option for various arc formats, you can try them all until you get the one that seems to give sensible results.

Hi folks,

I don't have any CNC machines yet and I am just learning Gcode, but I figured it
would help to look at code examples and try to plot them with the backplot in EMC.

The install was cake (I guess cause I teach Linux) but I can't get consistent results out of the backplot feature. Specifically the "3D_chips.ngc" file seems to plot way off the screen an when I try to scroll, the backplot screen is blank. Also is there anyway to just to do a quick backplot without attempting to control the machine? In other words how do I speed things up?

I'm using sim.run from a shell window
and the BDI-TNG which uses RTAI and Redhat 7.2 on a PII600 with 128M of RAM.

Thanks
Brian

I think I read in the EMC handbooks that 3dchips ngc was a test for a machine with more thsan 3 axis? I had that happend with me too.
The Z on that last cut was acting like a X & Y traveling way to far out.

That backplot someday will improve.
But hey it's free right?